>The point was that i don't have to learn something only to learn that i didn't need to learn it in the first place.
I was looking at more from the point of view of being a large hole in your knowledge base, and one that's likely to get really important soon. I know when I learned my first functional language, Ocaml, it was a really mind bending experience. It took me about a week to finally "get it", where as normally languages are so similar that a couple of hours is easily enough to grasp all the concepts, the rest of time is just getting faster.
With many common languages, "learning" the language has more to do with learning APIs and minor syntactic quirks. You'll learn more if you chase after languages with very different models of computation.
Languages I've found particularly mind-blowing: Perl (esp. coming from C++), Scheme, OCaml, Prolog, Erlang, J / APL.
I was looking at more from the point of view of being a large hole in your knowledge base, and one that's likely to get really important soon. I know when I learned my first functional language, Ocaml, it was a really mind bending experience. It took me about a week to finally "get it", where as normally languages are so similar that a couple of hours is easily enough to grasp all the concepts, the rest of time is just getting faster.